BOYS will be boys and Jim Carrey will be Jim Carrey. Few other actors would have the guts to paint a big red smiling phallus on the poster of their latest film, in front of a stunned room of European press.

Jim Carrey was left drained and "exhausted" after embarking on an extreme diet to shed the pounds for his new film, I Love You Phillip Morris.

One scene shows the Mask star, who plays conman Steven Russell, lying on his prison bed with his rib cage protruding disturbingly from his bare chest.

"In the last week or so I was literally having this little tomato drink once in a while and I had water and supplements so I could stay alive but there was really nothing of substance", Jim said.

"In the last two days before the main shots where I look really skinny, I just stopped eating completely and had a little taste of water, like an African runner."

Jim, who plays a conman who escaped from prison four times in the US to be with his gay lover Phillip Morris, added: "I was completely exhausted during that part of it, I was completely raw, like an old man in the last two days, no energy whatsoever, it was sadistic."